On the logic of theory change: Safe contraction

This paper is concerned with formal aspects of the logic of theory change, :and in particular with the process of shrinking or contracting a theory to eliminate a proposition. It continues work in the area by the authors and Peter Gi~rdenfors. The paper defines a notion of "safe contraction" of a set of propositions, shows that it satisfies the Gi~rdenfors postulates for contraction and thus can be represented as a partial meet contraction, and studies its properties both in general and under ~arious natural constraints.